How much power a dehumidifier draws
Dehumidifier efficiency is rated as an Integrated Energy Factor (IEF): liters of water removed per kWh on the DOE test. So the power while the compressor runs is pints per day × 0.4732 ÷ IEF ÷ 24 kilowatts.
Worked example — 50 pints at IEF 2.02: 50 × 0.4732 = 23.7 L a day; ÷ 2.02 = 11.7 kWh a day; ÷ 24 h = 0.488 kW. Running nonstop at the U.S. average of 18.19¢/kWh that's $2.13 a day and $64.80 a month. With a humidistat switching the compressor off half the time, half that.
| Capacity (pints/day) | IEF used | Watts running | 24/7, per month | Half the time, per month |
|---|---|---|---|---|
| 20 pints | 1.92 | 205 | $27.28 | $13.64 |
| 30 pints | 1.92 | 308 | $40.91 | $20.46 |
| 35 pints | 2.02 | 342 | $45.37 | $22.68 |
| 50 pints | 2.02 | 488 | $64.81 | $32.41 |
IEF values are ENERGY STAR certified averages: 1.92 across all portables and 2.02 for units over 30 pints. Federal minimums since June 2019 are 1.30 up to 25 pints, 1.60 for 25–50 pints and 2.80 above 50 pints.
The pint ratings changed in 2019
Before June 2019 dehumidifiers were tested in 80°F air; now the test runs at 65°F, closer to a basement, and the same machine removes less water — so it carries a smaller number. ENERGY STAR's rough crosswalk: an old 30-pint unit ≈ 20 pints today, 50 ≈ 30, and 70 ≈ 40–45. Mixing an old pint rating with a new IEF overstates the watts, which is why the calculator asks which test the box uses.
How long will it run?
Plugged in around the clock, a dehumidifier on a humidistat runs its compressor only while the air is above the set point. A damp basement in summer may keep it running most of the time; a drier space far less. The calculator shows nonstop as the worst case plus a 25–75% range, or measure it: a plug-in meter over a few days gives the real kWh.
Ways to spend less
- Set the humidistat to around 50% instead of continuous.
- Drain to a floor drain or pump so the unit never sits idle on a full bucket and then has to catch up.
- Keep doors and windows to the space closed, and fix the moisture source — gutters, grading, a dryer vent — where you can.
- Clean the air filter regularly so the coil gets full airflow.
- When buying, compare IEF: a higher number removes more water per kWh.
Common mistakes
- Assuming 24/7 means full power 24/7. With a humidistat it cycles.
- Comparing an old 70-pint box to a new 50-pint one. On today's test the old unit is roughly a 40–45-pint machine.
- Ignoring the air conditioner. In living spaces central AC already removes moisture, and every watt a dehumidifier uses ends up as heat in the room.
See also the air conditioner cost calculator and your state's electricity rate.